The invention relates to a vessel, preferably a ship, for transport and mounting of structures, said vessel comprising a hull and at least four vertically elevational support legs as well as displacement means for elevating the support legs.
Such a vessel is known from for instance GB-A-2,120,607. In this specification a ship is described which is used for installation of large offshore structures. The ship is equipped with four elevationally movable legs and a rail device on the deck of the ship. However, the ship is specially designed in the sense that the four elevational support legs form an integral part of the vessel and accordingly are mounted through its deck. Moreover, use of the rail structure means that the ship can only be used when a structure is extended outward from the deck and is to be arranged on a platform on a level with the deck""s surface.
In connection with the mounting of windmills offshore it is furthermore known to transport same on a jack-up barge, which is towed out or which may perhaps sail on its own, and where only one mill at a time can be carried along, and where the speed of the transport unit is very limited. Such a jack-up is also very sensitive to wind conditions, for which reason it is only possible to erect the mills partly relatively dose to land and partly in relatively calm weather.
The object of the present invention is to provide a vessel which based on an existing vessel, i.e. complete with all gear, makes it possible to transport windmills and mount these mills on previously built structures on the seabed, and where the windmill erection itself will take place under the same conditions on land, and where the mounting may take place via cargo ships of the self-supplying type. The ship is in other words a unit which can handle all tasks comprising loading of the mill units, transport of several mill units to the mounting site, including lifting thereof from the cargo ship and lowering thereof to the preinstalled base on the seabed.
The ship is accordingly a cargo ship, preferably a container ship or a bulk carrier, to which certain structural additions have been made. The cargo ship distinguishes itself by holding a big cargo, which in this case will be up to 10 windmills, but at the same time also being highly seaworthy and able to maintain good speed, just as such a cargo ship holds the necessary facilities for the crew.
The object of the invention is achieved by a vessel of the type described in the preamble and where the support legs are furthermore mounted in at least two consoles which by first means are connected to the hull""s right and left long side, respectively, and where the vessel also comprises at least one auxiliary structure, preferably a crane, for handling and placing the structures below the waterline.
The system accordingly functions by securing the mentioned consoles to know vessels by means of first mans which for example may be a rail device. Through each console there is mounted one preferably two elevationally movable legs, said legs ensuring that the ship will remain stationary, even in rough sea. It should be noted that in connection with the handling of the windmills a locking of the legs will take place in that the ship is raised to the necessary level, whereupon a blocking takes place since a high wave would otherwise give rise to instability during handling of the mills. By means of the crane itself it is thus possible to handle the large windmills, and where on the deck there may furthermore be mounted additional auxiliary cranes to ensure loading to and from the quay.
By providing a vessel according to the invention, the support legs will slide relatively frictionless in the sleeve which partially encloses the support legs. The sleeve may as disclosed be coated with a friction reducing substance, preferably in the form of teflon, or the support legs may be coated with teflon for achieving the same function. Furthermore, the legs are adapted for the sleeve via a sliding fit since it is important that there is not too much clearance between sleeve and support leg.
By providing a vessel according to the invention, an appropriate method for adjusting the vertical position of the support legs is achieved, since the hydraulic system will provide for the correct pressure on the support legs. It should also be noted that each support leg preferably has two wire winches mounted on either side thereof. The number of windings on the wire winch indicates that gear ratio where a gear of 9 is preferably preferred in such a manner that when the wire winch produces a 35 ton load, the pressure which is produced via a hydraulic station on each support leg may reach up to approximately 300 tons.
By providing a vessel according to the invention, the pressure on each individual support leg may be measured and indicated via the load cell.
By providing a vessel according to the invention, it is possible to adjust the weight in such a manner that when a corner exerts a high pressure on the load cells, such as disclosed in claim 4, they will send a message to the control system to change the pressure diagonally opposite this unit. This is accomplished by removing liquid from the chambers in this corner and by pumping in liquid in the diagonally opposite corner, thus achieving a form of equilibrium and compensating for the load weight that is moved. This anti-heeling system may be active both when the ship is floating and when it is anchored on the seabed via the support legs. In the first instance, a liquid sensor and gyro function will register heelings of the ship and a signal is transmitted from the sensor to the anti-heeling system, thus ensuring the stability of the ship.
In the latter instance, where the liquid sensors are not functioning, the load cells mounted on the support legs will register any pressure and any change of pressure on the support legs, when a load is moved, and will signal this information to the anti-heeling system, which is thus activated and compensates for the differences in pressure.
By providing a vessel according to the invention, an appropriate size of the console itself is achieved such that good control of the support legs within the longitudinal sleeve is achieved, said sleeve being located inside the console, or which is obtained by means of the holes which are cut in the upper and lower surfaces of the console to provide an aperture through the support legs may slide.
By providing a vessel according to the invention, the console will make up a removable unit which thus an be dismounted from/mounted on the structures of the known vessel.